Multiaxial driving apparatus

1. A driving apparatus comprising: a converter circuit that converts an AC power supply to a DC power supply; a plurality of inverter circuits that are provided in parallel between positive and negative bus-bars that are connected respectively to positive and negative output terminals of the converter circuit, where each of the inverter circuits is configured by connecting a plurality of semiconductor switching elements in a series-parallel combination in a bridge configuration; a plurality of bus-voltage smoothing capacitors that are provided in parallel between the positive and negative bus-bars; and a control unit that controls an operation of the inverter circuits individually under a program control, the driving apparatus being capable of driving a motor by connecting the motor to an output terminal of each of the inverter circuits, wherein a reactor, and a switching device that does not rely on an electrical signal are provided, where one end of the reactor is connected to an output terminal of an inverter circuit, to which a motor is not connected, among the inverter circuits, and the other end of the reactor is connected to the switching device, a positive terminal of the bus-voltage smoothing capacitor for an inverter circuit, to which the reactor is connected, is disconnected from the positive bus-bar, and is connected to a switching base terminal in the switching device, one switching terminal in the switching device is connected to the other end of the reactor, and the other switching terminal in the switching device is connected to the positive bus-bar, and in the switching device, when the switching base terminal and the one switching terminal are connected through a conductor, and the switching base terminal and the other switching terminal are not connected, the inverter circuits, to which the motor is connected, receive a motor-control command from the control unit, and then uses the semiconductor-switching elements connected in a series-parallel combination in a bridge configuration to generate AC power with an arbitrary frequency and voltage, to be supplied to the motor, from a bus voltage generated by the corresponding bus-voltage smoothing capacitors whose positive terminal is connected to the positive bus-bar, and an inverter circuit, to which the reactor is connected, receives a power-assist command from the control unit, and then the semiconductor switching elements connected in a series-parallel combination in a bridge configuration operate as a buck-boost switching device to store power by an increase in the bus voltage in a bus-voltage smoothing capacitor for the corresponding inverter circuit, where the bus-voltage smoothing capacitor is connected at its positive terminal to the switching base terminal in the switching device.

2. The driving apparatus according to claim 1 , wherein the control unit includes, for each of the inverter circuits, a parameter that switches between a motor-control mode and a power-assist mode, a motor-control command generation unit that generates the motor-control command when the parameter designates a motor-control mode, and a power-assist command generation unit that generates the power-assist command, taking into account driving power in other inverter circuits when the parameter designates a power-assist mode.

3. The driving apparatus according to claim 1 , wherein a motor or one end of the reactor is electrically and switchably connected to an output terminal of the inverter circuit, to which the reactor is connected, by switching between the motor and the one end of the reactor through a different switching device that does not rely on an electrical signal, and the control unit outputs a motor-control command to the inverter circuit, to which the reactor is connected, when the motor is electrically connected thereto, and outputs a power-assist command to the one inverter circuit when the reactor is electrically connected thereto.

4. The driving apparatus according to claim 1 , wherein the control unit generates the motor-control command and the power-assist command in synchronization with each other based on a same calculation cycle.

5. The driving apparatus according to claim 1 , wherein each of the plurality of bus-voltage smoothing capacitors are configured by connecting N (N is an integer) bus-voltage smoothing capacitors in parallel.